1. Field of the Invention
The present invention relates to a tolerance display system, and more particularly, to a tolerance display system used by workers engaged in working on various products such as iron castings, open die forgings, aluminum alloy castings, steel castings, metallic sintered products, die castings, parts formed by shear working of sheet metal, and parts formed by press working of sheet metal. The display system displays general tolerance information without direct individual tolerance indication in manufacturing drawings, and limits of size calculated based on such drawings.
2. Description of the Related Art
In manufacturing drawings used in worksites in various manufacturing and machining industries, dimensional tolerances, for example, based on national standards are indicated. The general dimensional tolerance (permissible deviation in dimensions without tolerance indication) meant for simplifying indications in drawings have no individual tolerance indication and no tolerance indication for individual sizes on drawings, but are given collectively in the form of a list of standards. The general tolerance is mainly applied to the dimensions of parts that do not require particularly high precision in view of their functions.
In working at actual worksites, the general tolerance is still very important and indispensable information in manufacturing high quality products, but such information is not included in the dimensions given in drawings.
Meanwhile, conventionally, in worksites in various manufacturing and machining industries, general tolerances are known to workers only based on their sense and experience of many years or through a list of standards. In some cases, general tolerance values available from the standards list are used to calculate limits of size on paper or using a desktop calculator (hereinafter simply as a “calculator”), and the results are added or used for correction of the sizes given on the manufacture drawings.
According to the conventional method, however, the operation heavily depends on the experience and sense of workers, in other words on their memory. As a result, accurate limits of size are sometimes not available when the workers are in error. It is difficult and time consuming to review the standards list, carry out calculation on paper or using a calculator based on the obtained values of general tolerances, and then finally add or correct dimensions on the actual manufacture drawings. It is highly possible that workers may read incorrect values of general tolerances by mistake when they review the list. The standards lists are often kept at offices that are remote from worksites, or in reality they cannot easily be carried, in other words, they are not easy to use for the workers.
Therefore, in the conventional methods, accurate dimensional information necessary for producing high quality products, in other words, limits of size, are not readily and easily available to the workers.